What actually is damp?
Damp means different things to different people
Damp can be a musty smell in the air, mould appearing on walls, a tidemark on the wall, a cold feeling when you touch the walls, brown patches on the floor, walls or ceiling or condensation.
There are three types of damp
1. Rising Damp
Brown tidemarks, cold feeling on the wall
The above will normally stop at about one metre from the ground and only happen on walls that are in contact with the ground (this can be internal walls as well as external). This is called Rising Damp and is caused by the Damp Proof Course (DPC) either missing fully or partially and the brickwork coming in to contact with the soil.
The brickwork sucks up the water and this causes the damp marks on the wall. You will
need to contact a surveyor to get the DPC fixed but the resulting work will be expensive and will take time to plan and execute. In the meantime a dehumidifier will dry the air in the room which will mean that the wall will then release the moisture that it is holding into the room for the dehumidifier to suck in and process. Although the wall will start to suck water up again from the ground and the process will become cyclic, the dehumidifier will help to control the problem until the DPC can be fixed.
If a brown patch appears in the middle of a wall or on a wall not in contact with the ground.
This will be a leaking pipe and will need immediate attention from a plumber to find the source. If you do not cure this problem ASAP then at worst a ceiling could collapse! In the meantime a dehumidifier will help to dry out the effected area.
Anything else is caused by condensation.
Once you have identified and dealt with the causes of the damp then the smell will go as well. It is vital to remove the cause as soon as possible because the mould spores that come with damp are damaging to your health.